Capacitive Pressure Cell Temperature Shock Compensation
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Solution Overview
Problem
Capacitive pressure measuring cells face significant measurement errors due to rapid temperature changes, known as thermal shocks, which can lead to erroneous assumptions about mechanical damage or the need for device replacement, and existing compensation methods are delayed due to temperature sensor inertia.
Innovation Solution
A method that detects temperature shocks by monitoring the gradient of the difference in capacitance values between the measuring and reference capacitors, allowing for early compensation without relying on temperature sensors, using pre-stored compensation curves based on empirical data to quickly correct measurement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors are used to detect thermal shocks, then temperature measurement can be achieved, but the response is delayed due to sensor inertia
Solution Approach 1:
The patent replaces the mechanical/thermal temperature sensor system with an electrical measurement system. By measuring capacitance changes in the measuring capacitor and reference capacitor, the system detects temperature shocks electrically rather than thermally, eliminating the inertia inherent in thermal sensors and achieving immediate detection.
Solution Approach 2:
The patent introduces capacitance measurement as an intermediary parameter to detect temperature shocks. Instead of measuring temperature directly, the system measures capacitance changes that result from temperature-induced membrane deformation, providing an indirect but faster detection mechanism.
2Loss of time
If capacitance values are used to detect temperature shocks, then early detection is achieved, but differentiation from mechanical damage requires additional analysis
Solution Approach 1:
The patent employs feedback mechanisms by continuously monitoring the relationship between measuring capacitor capacitance and reference capacitor capacitance. By establishing expected relationships and comparing actual measurements against these expectations, the system provides feedback that helps distinguish between temperature-induced changes and mechanical damage.
Solution Approach 2:
The reference capacitor serves multiple functions: it provides a baseline for comparison, enables temperature shock detection through ratio analysis, and helps differentiate between thermal and mechanical effects. This multi-functional use of the reference capacitor simplifies the overall detection system while maintaining accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method significantly reduces temperature-related measurement errors by initiating compensation immediately after a shock, correcting errors before temperature sensors respond, and allows for a plausibility check using a temperature element to confirm the cause of the error.
Implementation Method 1
When pressure is applied, the membrane is deformed, which results in a change in the capacitance of the measuring capacitor
Implementation Method 2
a temperature jump is detected if the measured value of the reference capacitance is outside a tolerance range around an expected value... result from a temperature difference between a medium acting on the membrane and the base body
Data Source
AI summary
A method for compensating a temperature shock at a capacitive pressure measuring cell is disclosed, the method employs a measuring capacitor and a reference capacitor, wherein in an evaluation unit a pressure measurement value p is obtained by forming the quotient Q from the capacitance values of the reference capacitor and the measuring capacitor and a pressure measurement value pM is obtained by use of the measuring capacitor, wherein the temperature shock is detected by comparing the pressure measurement values p and pM with each other and monitoring the gradient dD of the difference value D of the two values with respect to exceeding a predetermined threshold value. The intensity of the temperature shock is determined based on the gradient dD of the difference value D, whereby the influence of error can be counteracted very quickly and the duration of the influence of error is also very short.